The present invention relates to a substrate treatment system provided with an air conditioning function for controlling the treatment environment of a semiconductor wafer or an LCD substrate.
In the photolithography process for fabricating a semiconductor device, photoresist is applied to a semiconductor wafer, the applied resist is pattern-exposed, the pattern-exposed resist is developed, and the developer is washed away with water. A series of these treatments is performed in an air-conditioned resist treatment system in a clean room.
A conventional resist treatment system has a fan filter unit (FFU) constituted by integrating a fan with a filter on its upper side. In the FFU, particles contained in air are removed and clean air is downflow-supplied toward each treatment unit. Moreover, a chemical filter is set to the upstream side of the FFU and thereby, organic components and ions contained in air are removed.
Recently, the so-called chemically-amplifying-type resist is frequently used in a photolithography process. The chemically-amplifying-type resist easily reacts on a very small amount of alkaline component such as ammonia contained in air. When the chemically-amplifying-type resist reacts on ammonia, a neutralization layer is formed. Because the neutralization layer is not easily dissolved by a developer, a designed pattern circuit is not formed. Therefore, it is necessary to lower the ammonia concentration of the air to be supplied to a process section up to a harmless level. However, the chemical filter has a short element service life and therefore, a filter element must be frequently replaced, the serviceability ratio of the system is lowered. The running cost is increased since it is necessary to periodically measure the ammonia concentration and estimate the life of the chemical filter element. Furthermore, the chemical filter is expensive.